Electrical heaters

ABSTRACT

An electrical heater for use in heating the engine, battery, seat or rear window of an automobile includes a thin, flexible rectangular heating pad embodying a composite electrical resistance sheet, a time switch mounted on the pad at a corner thereof and a pair of leads extending from the corner to provide for the operative connection of the heater to the vehicle battery. The pad comprises a resistance sheet composed of a flexible substrate of glass cloth having a coating of electrically resistive material on one surface. Header and distributor conductors an electrical contact with the face of the coating and connectable to said leads through the time switch are formed by a pair of elongated flexible braided wire electrodes extending sinuously across the coating and stitched to the sheet. Each electrode forms a plurality of U-shaped portions. The electrodes cross each other near their U-bases so that longitudinal stretches of one electrode alternate with longitudinal stretches of the other. The electrodes are electrically insulated from each other at the crossings.

United States Patent [72] Inventor Joseph ThomasQuinn [54] ELECTRICAL HEATERS 5 Claims, 3 Drawing Figs.

[52] US. Cl 219/529, 219/202, 219/211, 219/358, 219/549, 338/211, 338/308 [51] Int. Cl 1105b 1/02, HOSb 3/34 [50] Field of Smrch '219/345,

[56] References Cited umrso STATES PATENTS 1,534,220 4/1925 Kercher 219/208 2,392,712 1/1946 Woodman 219/529 Primary ExaminerA. Bartis Attorney-Mason, Fenwick & Lawrence ABSTRACT: An electrical heater for use in heating the engine, battery, seat or rear window of an automobile includes a thin, flexible rectangular heating pad embodying a composite electrical resistance sheet, a time switch mounted on the pad at a comer thereof and a pair of leads extending from the corner to provide for the operative connection of the heater to the vehicle battery. The pad comprises a resistance sheet composed of a flexible substrate of glass cloth having a coating of electrically resistive material on one surface. Header and distributor conductors an electrical contact with the face of the coating and connectable to said leads through the time switch are formed by a pair of elongated flexible braided wire electrodes extending sinuously across the coating and stitched to the sheet. Each electrode forms a plurality of U-shaped portions. The electrodes cross each other near their U-bases so that longitudinal stretches of one electrode alternate with 1ongitudinal stretches of the other. The electrodes are electrically insulated from each other at the crossings.

PATENTED JUL2OI97I 3,594; 547

JDSBPH THOMAS QU N 6" Cum w A llorneys PATENTED JUL20 197i sum 2 UF 2 lnvenl n' Jose-PH HOMAS Qumu B Wa m mm&i%m

J V Attorneys ELECTRICAL HEATERS This invention relates to electrical heaters,the chief object being to provide an electrical heater which operates efficiently with a low voltage electricity supply, for example, with the usual l2-volt battery of a motor vehicle.

According to the present invention, an electrical heater includes a heater element comprising a flexible sheet composed of a base layer of electrically insulative material and a coating of electrically resistive conducting material on the base layer, a pair of elongated flexible electrodes of braided wire in electrical contact with the face of the coating, each of the electrodes extending sinuously across the coating width in a plurality of elongated U-portions and one of the electrodes crossing the other near the U-bases so that longitudinal stretches of one electrode alternate with the longitudinal stretches of the other electrode, pieces of electrically insulative material between electrodes at the crossings, stitching securing the electrodesto the sheet, and means for connecting the electrodes to a power source.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: t

P10. 1 is a front view of. an electrical heater for connection to the battery of a motor vehicle,

FIG. 2 is a sectional view on the line ll-Il of FIG. 1, and FIG. 3 is a fragmentary sectional view on the line lll-lll of FIG. 1.

Referring to the drawings:

An electrical heater for use in a motor vehicle having the usual l2-volt battery includes a thin, flexible, insulated rectangular heating element or pad embodying a composite electrical resistancesheet'll, a time switch 12 mounted on the pad at a corner thereof, and a pair of external leads 13 and 14 extending from said corner of the pad to provide for the operative connection of the heater to the battery.

The resistance sheet 11 is composed of a base layer of glass cloth [5 and a coat of thermally stable, electricityconducting material 16, such as a rubberlike polymer or a silicone rubber, formed on the surface of the cloth [5. A suitable resistance sheet of this kind is supplied by Imperial Chemical Industries Limited under the Trade Mark Flexel." The conducting coat 16 may be applied to the face of the cloth by roller. The thickness of the composite sheet 11 is approximately 0.008 inch. Flexible reinforcing strips 17 and 18 of insulating material are stitched to the ends of the sheet 11, against the coat l6; and a rectangular, flexible reinforcing patch 19 of insulating material is stitched to the sheet 11 at a corner thereof and against the coat l6.

, A pair of elongated electrodes 20 and 2] are stitched to the sheet 11 and to the end reinforcements thereof so as to lie on the face of the coat 16. The electrodes consist of a pair of lengths of flat, braided metal wire, each length extending sinuously across the sheet width in a plurality of elongated, substantially rectangular U-portions (FIG. 2). The electrode 21 overlaps the electrode 20 at the U-bends, so that the longitudinal stretches 21A of the electrode 21 alternate with the longitudinal stretches 20A of the electrode 20, and a pair of ends 208 and 21B of the electrodes are located adjacent to the comer reinforcing patch 19. Insulating patches 22 of flexible material are provided between the electrodes at the U-bends thereof, being stitched with electrode 21 to the reinforced ends of the sheet 11. The stitching of the strips, patches and electrodes is of a polyester/cotton thread. The distance between the reinforcing strips 17 and 18 is about l8 inches, and the electrode stretches 20A and 21A divide the coat 16 into a plurality of longitudinal side-by-side resistance strips R each about 2 inches wide.

A sealed, rectangular, electrically insulating envelope 23 neatly houses the resistance sheet 11 to form therewith the pad 10; the envelope is formed by welding together the edges of two superposed rectangular sheets of black, heavy-duty pol thene.

he time switch 12 mounted on the pad 10 includes a 12- hour clock composed of a cylindrical casing 24 penetrating a circular opening in the patch-reinforced corner of the pad, a pair of short internal leads 25 and 26 extending through an opening in the casing, and a square face portion 27 closing the casing and forming a flange thereon. The lead 25 is connected to the adjacent end 203 of the electrode 20, and the lead 26 is connected to the external lead 13 which is connectable to the positive terminal of the vehicle battery by a suitable clip. The external lead 14 is connected at one end to the end 213 of the electrode 21 and is connectable at the other end to the vehicle chassis by a suitable clip. The face portion 27 has thereon at its rear a set of four studs 28 penetrating the reinforced corner of the pad and penetrating also an annular backplate 29 extending around the casing and engaging the rear of the pad. Nuts 30 on the studs provide for clamping of the pad between the flange 27 and the blackplate 29 so that the clock is securely mounted on the pad.

The envelope is fitted at the corners with adhesive pads 31 to enable mounting of the heater in any desired position in the vehicle. Alternatively, the envelope is fitted with eyelets, loops or other means enabling suspension of the heater in the vehicle.

In use of the heater say to protect the automobile battery and electrics from the effect of overnight frost and condensation and so facilitate starting of the automobile, the clock is set to close the switch in the heating circuit at a suitable time e.g. a few hours before the starting time, the heater is mounted in a suitable position under the engine bonnet, and the external leads are'clipped to the battery and to the chassis. Following the timed closure of the switch, the heater runs at 4.5 amperes per hour to produce 50 watts of radiant heat under the bonnet.

The heater may alternatively be used as a seat heater, or may be placed on the back-window ledge to prevent misting of the back window.

Clearly the heater has a wide field of use where only a low voltage electrical supply is available.

We claim:

I. An electrical heater including a heater element comprising a flexible sheet composed of abase layer of electrically insulative material and a coating of electrically resistive conducting material on the base layer, a pair of elongated flexible electrodes of braided wire in electrical contact with the face of the coating, each of the electrodes extending sinuously across the coating width in a plurality of elongated U-portions and one of the electrodes crossing the other near the U-bases so that longitudinal stretches of one electrode alternate with the longitudinal stretches of the other electrode, pieces of electrically insulative material between electrodes at the crossings, stitching securing the electrodes to the sheet, and means for connecting the electrodes to a power source.

2. An electrical heater according to claim 1, wherein the heating element includes a cover of electrically insulative flexible material enclosing the flexible sheet.

3. An electrical heater according to claim 1, including a time switch mounted on the heating element and in circuit with the electrodes to control the current flow through the sheet.

4. A heater according to claim 3, wherein the time switch is mounted on the heating element at a corner thereof, and a pair of external supply leads extend from said corner.

5. A heater according to claim 4, wherein the time switch is connected to one electrode and to an external lead connectable to the positive terminal of a vehicle battery, and the other external lead is connected to the other electrode and is connectable to the vehicle chassis. 

1. An electrical heater including a heater element comprising a flexible sheet composed of a base layer of electrically insulative material and a coating of electrically resistive conducting material on the base layer, a pair of elongated flexible electrodes of braided wire in electrical contact with the face of the coating, each of the electrodes extending sinuously across the coating width in a plurality of elongated Uportions and one of the electrodes crossing the other near the Ubases so that longitudinal stretches of one electrode alternate with the longitudinal stretches of the other electrode, pieces of electrically insulative material between electrodes at the crossings, stitching securing the electrodes to the sheet, and means for connecting the electrodes to a power source.
 2. An electrical heater according to claim 1, wherein the heating element includes a cover of electrically insulative flexible material enclosing the flexible sheet.
 3. An electrical heater according to claim 1, including a time switch mounted on the heating element and in circuit with the electrodes to control the current flow through the sheet.
 4. A heater according to claim 3, wherein the time switch is mounted on the heating element at a corner thereof, and a pair of external supply leads extend from said corner.
 5. A heater according to claim 4, wherein the time switch is connected to one electrode and to an external lead connectable to the positive terminal of a vehicle battery, and the other external lead is connected to the other electrode and is connectable to the vehicle chassis. 